Using the car's radio, turn it to AM and tune it to the lowest number then lower the volume. Alternator charging voltage can be checked using a digital multimeter at the battery terminals. If a diode is gone bad, part of the VAC waveform will leak past the bad diode causing an AC ripple. You can start by replacing the 12V battery, but I doubt that is causing the DTC that your car logged - so you'll probably end up replacing the traction battery if you decide to keep the car. Drove for a few days with a bad alternator, dropping kids off at school and at my parents 20 minutes away before driving another 20 minutes to my favorite mechanic. If you have a dead alternator,and a fully charged battery how far can you drive it without running any accessories?. This is the amount of time the battery will supply the vehicles electricals so the vehicle can continue to run in the event the charging system should fail. Some say anything over 13v with car running is ok. He can replace the alternator all he wants, but if he does not repair the oil leak the problem will continue. It demonstrates that the alternator cannot keep a charge when the car is running. A battery with a short in it will cause the alternator to run at full output for extended periods of time, if not continuously - and they are not built to do this. There is not a set up out there on stock electrical system running over 1200 true watts of power, and adding batteries can get you there but at the expense of your alternator. An alternator charges a vehicle's battery. The wire supplying the field current is often referred to as the "exciter" wire. There's a full 12volts on the battery. Alright, so if you suspect you have issues with your alternator and charging system in general, the first thing you need to rule out is a bad battery. 22 Answer s. Last month's article dealt with the principles of DC electricity and how your car's battery functions. Also there is a regulator controlling the charging current from the alternator to the battery when the car is running. It is not uncommon for a 160 amp alternator to have a continuous duty cycle of less than 90 amps. If the above steps reveal that the battery is working, it’s time to take a closer look at the alternator. Elements of Electrical Systems Waite Park, MN Alternator Inspections. Should be 13. Sure, you can use your car's battery when the alternator goes bad. Also, you can avoid the most common mistake made when testing an alternator of disconnecting the negative terminal of the battery while the engine is running. I normally try to replace tensioners every few belt changes on the alternator belt as they go bad over time especially if a worn belt is left on the tensioner for too long. But, I found out that this not the case. The next time you start your car the alternator will have to produce more energy than ever to make up the electrical loss of the slipping belt. No, it would be to see how the belt runs between the engine an alternator, and whether the tensioner is all running true, as well as whether I can pull start it easily enough when it's also turning the belt and alternator. A battery with a short in it will cause the alternator to run at full output for extended periods of time, if not continuously - and they are not built to do this. If your car continues to run with only the positive terminal connected, your battery is bad and won’t hold a charge. 2 ALL CYLINDERS: Try the following fixes. If the battery checks out, it's time to look at the alternator. The battery, alternator and fuel pump aren't the only culprits when your car dies off you while driving. There are only a few ways an alternator can go bad, but they tend to happen suddenly without a lot of warning. Can a bad battery actually stop a running engine? I know that you need electrical power to spark, but I was under the impression that the alternator would provide that, and that disconnecting the battery from a running car would not cause the engine to die. So a bad alternator doesn't necessarily mean a tow truck should be called right away. I'm coupling a big (180A) car alternator to a Honda engine to make a generator I was just wondering if I'd be OK to run it to check belt run and tensioner before I add a battery and excitation wire. How long can a truck run on a new battery with a bad alternator? My bf is 3. Unfortunately, car batteries need a DC voltage to supply to the car’s electrical components, therefore the electricity produced by the alternator has to change state. Car Audio Noise. 2 volts at the alternator terminal. Number 1 - Bad Battery. A battery with a short in it will cause the alternator to run at full output for extended periods of time, if not continuously - and they are not built to do this. That is because the battery has some reserve power in it, enough to keep the engine running for quite some time, many many miles in fact. When I shut lights, etc. Also, making that kind of alternator test is a bad idea. 8 volts, the voltage actually getting to the plus side of the coil is around 8-10 volts. After he can't jump start your car, he puts in his own known good battery and starts your car. off, engine still running, meter reading drops to 14. If you have a dead alternator,and a fully charged battery how far can you drive it without running any accessories?. You might notice that the battery cranks the engine over more slowly at times. Which is much cheaper than a new alternator and a tow truck bill. This is especially true if you play the radio and lights while driving. Taking the positive battery terminal off with the engine running is very bad for the alternator and the electronics in the carit can send a massive spike to the altetnator and electroncis, enough to fry the diodes in the alternator and fry the computor. Most auto parts stores will test them for ya to. He will tell you exactly if the alternator is in a good or bad condition, or if it needs replacement. If our e-fan really saved 1HP from the shaft of the engine, it would be drawing almost 100A from the electrical system of the car to do the same work! We can see that this is not the case, especially in a car with a 70A/90A alternator. With the electronic systems installed in today's vehicles, they can be damaged with voltage spikes coming from the alternator when disconnecting the battery. 5 mm [1/16th inch] apart), is (almost) filled with water. 2 volts at the alternator terminal. 1995 mustang GT Car just hit 100K miles 2 weeks ago. So a bad alternator doesn't necessarily mean a tow truck should be called right away. On most cars it should not be possible to move the car more than 13mm. Also, you can avoid the most common mistake made when testing an alternator of disconnecting the negative terminal of the battery while the engine is running. If your car stops after the jump cables are removed, then it is a problem with the car battery not charging. The display should now read one volt over the initial reading. It's a good possibility that it's the alternator right?. Also, making that kind of alternator test is a bad idea. If the dashboard gradually dims, the alternator is likely at fault. Common Symptoms Of A BAD Alternator. How much will it cost to fix a battery or alternator Changing out your battery is a fix that you can usually do on your own. The alternator is a pivotal piece of machinery when it comes to your car, truck, or SUV. A properly working alternator can often recharge a dead battery by running the automobile for a period of time. A bad cell can cause the generator/alternator to overcharge the other cells which will trigger the generator light in the speedo. If the alternator is bad the battery will keep the car running for quite a while. Signs of a bad alternator. Not to mention that this is a really, really bad way of checking for a bad alternator. One of the easiest and most beneficial upgrades you can do to get the most out of your ride, is to upgrade the ignition system. Why service is necessary: Issues can be pinpointed early and determined to be battery issues, cable or belt problems, or also the alternator itself. A Properly functioning Alternator. Do not run the alternator without being connected properly from the B+ terminal to the positive battery terminal. easier diagnostics of what the possible malfunction may be; You can make this check even if everything is OK with your car, it can't hurt. To prevent more failing of your electrical system, a bad alternator can easily strain the battery power, as an example, see to it. In general, the alternator shouldn’t require any regular maintenance and will usually run for up to 12 years without the need for any repairs. If the dashboard gradually dims, the alternator is likely at fault. When storing sulfate batteries, it is important a person to ensure that they are always charged, preferably to the maximum. If it's in the range, it's good. Anyway, I think it's the alternator, because a friend told me that if you unplug the battery while the car is on and it shuts off, the alternator is bad. Overrunning Alternator Pulleys (OAP) are used on a number of late-model import and domestic vehicles. Elements of Electrical Systems Waite Park, MN Alternator Inspections. A mechanic can easily replace the belt. Shopsarahmac sells a wide range of items, from dress, electronic, accessories to all another products. In older cars (before about 1964) this was done with a generator. The car alternator is used to charge the battery and power the electrical system while the car is running. Also, making that kind of alternator test is a bad idea. In fact, the alternator serves as the charger for the battery as well. Used only for those that require the stock connector to fit snugly. If you can drive it, go to the mechanic or auto parts store, they will most likely check it for free. Belt still intact, I. 4V is plenty to keep the car running. Alternator whine is caused by a difference in electrical potential (voltage) between two points. Along with recharging your car battery, the alternator powers all sorts of other electric systems in your car. While this can tell you how much electrical power the car is consuming, it will tell you nothing about the state of the battery or the generator. A dead alternator can cause all kinds of headaches, but how can you tell if your alternator is going out before it is too late? When you try to start your car and you hear a clicking sound, that signals your vehicle is dead you are left with several options as to why. Note: you can often mist the ignition system with water to help sparks from failed equipment show up. Checking the alternator is a relatively easy process. When a belt isn't turning freely, excess friction can cause the belt to heat up which can produce a smell similar to burning rubber. If it DOESN'T go to 15-16 volts then the brushes are in need of replacement or you have a bad diode or two. What is a one wire alternator? How much amperage do I need? Amperage Load Calculator. If you can jumpstart your car and it stays running, your battery is out of service. It's easy to tell when your car is having problems, but figuring out the cause of those problems can get confusing. Top 10 Signs of Alternator Problems. If you put two and two together you quickly realize that a bad alternator means a dead. Alternator Checks. "There are a lot of things drivers can do that causes their alternator to go out," Waits says. Don't forget that there are other possible reasons for an alternator not to work beside the alternator itself being bad. A) A bad alternator will result in a discharged (dead) battery and cause a vehicle to not start or run. If your battery goes dead, have the alternator checked when replacing the battery so it doesn't happen again. If you have a loose ground on the charging circuit the alternator current cannot go through the battery terminals as much as it should. This can wreak havoc and cause other circuits to malfunction. Number 1 - Bad Battery. You can start by replacing the 12V battery, but I doubt that is causing the DTC that your car logged - so you'll probably end up replacing the traction battery if you decide to keep the car. Test the Alternator Diode; To check for a bad alternator diode, you may want to reset your voltmeter to the lowest possible AC voltage scale setting. "People could jump start the car the wrong way, or install an accessory inside that overloads it. Although the battery can keep the vehicle running for a little while, it will not be able to keep it running for an extended period of time if the alternator malfunctions. If ever the person gladly avails these, it bad credit loan car is easy to prefer to spend forth, if they are not, you ought to have a 2nd thought. If your car continues to run with only the positive terminal connected, your battery is bad and won’t hold a charge. You can home test to see if its charging at all. Common Symptoms Of A BAD Alternator. Stop vehicle & check immediately If not belt look for a connection that just came off. The battery serves as a backup. However, the engine will stall as soon as the battery charge is. 2 ALL CYLINDERS: Try the following fixes. Run the engine and open your ears to how the alternator sounds. Buy AUTDER Car Battery Tester 12V 6 LED Lights Digital Alternator Tester, Test Battery Condition & Alternator Charging Tester for Car Motorcycle: Battery Testers - Amazon. Bad alternator sound can be confused with bad power steer pump noise. An alternator problem can quickly drain your battery, so if you see a warning light on your system, take your car in for service as soon as possible. If you have a loose ground on the charging circuit the alternator current cannot go through the battery terminals as much as it should. The alternators job is to provide power to your vehicles accessories (headlights, stereo, etc) through induction. if you get the car started, you can drive wherever, just dont turn it off till you fet there. The first item to check would be the alternator. This test is to see if you can wake up the voltage regulator, it it can not be woke up, the Reg is bad or you have corroded wires. OAP pulleys have a one-way clutch inside the center of the pulley that slips and allows the pulley to free-wheel when engine speed suddenly drops. On some cars this is all sampled and done 100% in the alternator's internal voltage regulator. Why service is necessary: Issues can be pinpointed early and determined to be battery issues, cable or belt problems, or also the alternator itself. Run your car at tick over then switch on the lights and then the fan you can hear the engine note change as the alternator kicks in. Yes, absolutely. Take it somewhere good and have it tested. If it is a bad alternator, then your vehicle won't stay on. depends on the reserve of the battery, most batteries have about a 90 min. Anything higher is also bad too. while the engine is not running? What happens when you turn the key?. As for keeping it running, once the car car is running all you need is less electrical draw than what the alternator can put out. Side note: You can take a good brand new battery with no help from a vehicle's alternator to maintain it and it will run for a period of time till it's charge runs too low to run the vehicle. If the alternator is not working properly, even the best car battery will eventually run down. It should be between 13. When below 13, car is running off the battery only. Replace cap and rotor. Please Settle a bet. Pin 2 of the push in connector on the alternator use 18 ga wire In the above pictures, you can see a black wire that is connected to the alternator mounting bracket. The battery serves as a backup. This is why adding a second battery provides you with more power when the car is off and upgrading to a high output alternator helps when it's on. 2 volts at the alternator terminal. If this circuit, including the indicator LED, is faulty no Pre Induction can take place. If you have experienced or observed most or all of the signs discussed in the steps above, your car\'s alternator needs to be fixed or replaced as soon as possible. Once you've identified the circuit at fault, determine which electrical items are powered by that circuit. 5 volts with a good alternator. The wire supplying the field current is often referred to as the "exciter" wire. And the alternator does charge the battery if it is low on charge. Do this at your own risk of course. On the other hand, worn out or broken bearings can cause disturbing noises when running your vehicle. An alternator charges a vehicle's battery. Can a car run with a bad alternator, If a jump starts and keeps your car running, but the car can't start again off of its own There are certain signs of a bad alternator to look for. Most part stores can test an alternator. Basically, your battery gets the engine going, but once it’s on, the alternator takes over and can, in theory, continue running the car without the battery’s help. A properly working alternator can often recharge a dead battery by running the automobile for a period of time. If the alternator is going or has gone bad, in most cases the vehicle can be driven for a short distance and for a short period of time, allowing you to make it to a service station or automotive parts store for. Signs of a Bad Alternator. "Easily 50 percent of an old car's electrical problems can be traced to bad grounds," Zitren said. That is why you can jump start a car and run it @ highway speed for 20 minutes or so & the battery, if it is good, will be @ full charge. Best Answer: Yes that can cause your car to not run. You can carefully tap it with a hammer while the car engine is running while checking it with a multimeter to see if the voltage is changing. Its a 15 year old car with a 15 year old alternator. After he can't jump start your car, he puts in his own known good battery and starts your car. I'd have a booster battery pack ready for restarts tho. A good voltage while the car is off and has not been running for a few hours (idle voltage) is ~>=12. They're designed to provide your vehicle with enough electrical oomph to start by juicing the starter motor with a surge of power and getting the whole works spinning. Alternator Whine in Car Audio. You skipped that second cup of coffee. Take it to a parts shop that has a roll-out or hand-held alternator/battery tester. If you put two and two together you quickly realize that a bad alternator means a dead. And some cars like Chrysler, Dodge, or Jeep the ECU completely controls the voltage and field input. There are a few things to inspect, such as: a broken terminal, bulge or bump in the case, crack or rupture of the case, excessive leaking, and discoloration. How much will it cost to fix a battery or alternator Changing out your battery is a fix that you can usually do on your own. In fact, it will charge the battery. So bad alternator is a possibility - but the idiot light does not light up - and the AutoZone alternator test was good. Alternators the world over are built to supply an initial high current, tapering back as the current used to start the vehicle is replenished. Alternator test with a voltmeter. -Car doesn't drain the battery while its off. Hook a volt meter to the battery terminals and while car is running it should read 14. (However, it isn't helpful to the engine to run it for long periods of time under low load. What controls the voltage out an alternator is the car's battery being in parallel with the output. It is not uncommon for a 160 amp alternator to have a continuous duty cycle of less than 90 amps. Then try to crank over the bad battery’s car once again. If it’s worn or loose, you may hear a squealing noise when you first start the car, and the alternator won’t operate properly, even though the alternator itself may be fine. Bad battery or bad alternator, Running car with no alternator - improved wiring. A failing alternator will start to make a loud whining noise at idle and the whining noise will increase with engine speed. It really can be quite a pain sometimes when it comes to belt noises. Basically, your battery gets the engine going, but once it’s on, the alternator takes over and can, in theory, continue running the car without the battery’s help. This might be a surprise to some people since the battery is such an important part, but as long as the car is running the alternator can provide enough power to keep it running and power the different systems. In normal operation, this diode allows power to flow one way, from the alternator to the battery. An alternator is a maintenance-free unit. Can I spin the alternator to charge a dead battery? I read somewhere in the comments (to a post about using a 12V cordless drill battery to charge a dead car battery) a reply saying to hook up the drill to the alternator and spin it fast to charge the battery. I have a 2004 Volvo C70. Adjust it if necessary by means of the adjustment strap on the alternator. If they weren't working, and the engine needed power from the battery to run the spark plugs, the engine would die. 2 volts, the Alternator probably has one or more Bad Diodes. The fact that the battery read over 13 volts after driving it indicates that the alternator works at least some of the time. So you need an alternator, and you need to save money? You can get a rebuilt alternator and save some money without losing reliability. Usually, the problem falls into. For instance, installing a power amp that draws 70 or more amps in a car that shipped from the factory with a basic stereo, could cause huge problems if the alternator is only capable of putting out 60A to begin with. I told my daughter (her car) I was 98% sure it was just a bad battery - but it is possible something else is wrong. 1) The generator (alternator) creates VAC which is then rectified into VDC. leads on the battery to see what the voltage is. If the alternator is going or has gone bad, in most cases the vehicle can be driven for a short distance and for a short period of time, allowing you to make it to a service station or automotive parts store for. 4V is plenty to keep the car running. Other Functions The alternator provides power for the electrical components. What can happen in this case is that the alternator can still supply power to charge the battery to start the car, but insufficient to charge the battery and supply a heavy electrical load- lights, air conditioning, stereo, wipers, rear window heater, turn signal etc. It is the job of the battery to provide the power to crank the engine and start the vehicle, however, it is the job of the alternator to make sure that the battery stays charged. If you live near one of our stores our automotive service staff will be happy to help you diagnose and fix such issues so you can get back on the road again!. The alternator recycles the power your car battery uses while driving, restoring the power it has lost while supplying the climate, engine management, entertainment and host of other systems with the power they need to run correctly. Most people think that if a battery is dead, the car won't start. If your car stops after the jump cables are removed, then it is a problem with the car battery not charging. It is not uncommon for a 160 amp alternator to have a continuous duty cycle of less than 90 amps. If you catch the alternator quickly, you can usually save the battery and save your money. They're designed to provide your vehicle with enough electrical oomph to start by juicing the starter motor with a surge of power and getting the whole works spinning. I had a dead battery in May, replaced it, found the new one soon dead in June, determined the alternator was the problem, replaced the voltage regulator in July, and ran fine for three weeks. I’m actually gonna park the car in this would be a first for me back the car and jump from the truck to the truck. com FREE DELIVERY possible on eligible purchases. How long can a car run with a bad Truck Alternator. I was told using this test, that if the car stays running with a battery cable pulled off, then this indicates the battery is bad. Having this happen on the side of a busy road or highway can create a lot of problems. But how do you know which part is causing your issue? All these parts work together to power your vehicle so it can be hard to know which part is at fault. Next, test the alternator and pay close attention to the condition of its diodes. If the vehicle requires more electrical power than the charging system – alternator – can provide, the battery covers the difference. Now the belt squeaks. There is nothing more frustrating than a dead car. I also notice a rough idle when those lights are on. Because the alternator is connected to (and critical for) other vehicle systems, any mechanical auto problems can have an effect on its function and have an effect on diagnosing car problems. You can home test to see if its charging at all. The battery would have kept the engine running and the red battery indicator light would have. 5 Bad Symptoms. If you continue to run with a weak alternator, be prepared to also have to shell out the money for a new battery, as you're going to kill the one in the car. In fact, the alternator serves as the charger for the battery as well. Just an fyi, a bad diode in the alternator can drain the battery even when the engine is not running. Bad alternator vs bad battery, which one is worse should not be the question. my car shut off while I was driving and then started back up and shut off again a few minutes later. If it's worn or loose, you may hear a squealing noise when you first start the car, and the alternator won't operate properly, even though the alternator itself may be fine. This article originally appeared on YourMechanic. A lot of people have trouble distinguishing the symptoms of a bad battery versus a bad alternator. A bad regulator can act up every so often, so when your testing it it may very well be working at that time of testing. 8 to about 14 volts on the battery with the motor running. The first system is the one we are concerned with. It would seem even worse if your car’s components are also running. Whether it's your daily driver, a weekend warrior, or that show car sitting in the corner of the garage. It's a good possibility that it's the alternator right?. After running fine for 15-20 minutes my alternator will begin to heat up until the point where it is too hot to even touch. How long can you drive a car with a broken alternator with a freshly charged battery? [more inside] I picked up a POS car a month or so ago because my previous car got destroyed in a freak snow/hail/rain storm/flood (in L. So you need an alternator, and you need to save money? You can get a rebuilt alternator and save some money without losing reliability. Check the alternator gauge. Elements of Electrical Systems Waite Park, MN Alternator Inspections. It allocates this power as the engine is going. Basically, your battery gets the engine going, but once it's on, the alternator takes over and can, in theory, continue running the car without the battery's help. This way, you get a great car part without shelling out a ton of dough. This article will discuss proper phasing of the speakers to achieve the maximum bass response out of your speakers, as well as proper power and ground procedures to allow your vehicle to achieve the maximum voltage output to your amplifier. Paying attention to the 10 trouble signs on this list can make it a little easier to diagnose car trouble caused by the alternator. Run your car at tick over then switch on the lights and then the fan you can hear the engine note change as the alternator kicks in. It should have the same voltage as at the alternator. Also the alternator bushings can go bad, which can mess with it’s geometry causing odd noises. After he can't jump start your car, he puts in his own known good battery and starts your car. Broken or loose terminals are dangerous, and can cause a short circuit. Using the alternator to deal with such a depleted battery can actually damage your alternator. Connect the capacitor lead to the output terminal of the dynamo or alternator. If your car will not start and you think you have a bad battery, alternator or starter, have your car inspected by a professional mechanic. Don’t be too hasty: The battery might be OK, but if the alternator can’t generate the juice to recharge it, the battery eventually will run out of power, and your car will stop running. This means it's important to distinguish between a weak battery and a bad alternator. You could do that with a bad battery, but a bad alternator limits you to however many amps the battery holds / amps drawn while driving. Option three is to purchase a new alternator or add a second alternator [link to running two alternators article] to your charging system. All in all, what I'm trying to say here, is that you should probably go to a different mechanic and have the alternator checked out before this guy stiffs you. The belt is louder than usual. Pin 2 of the push in connector on the alternator use 18 ga wire In the above pictures, you can see a black wire that is connected to the alternator mounting bracket. Connect the voltmeter probes on their respective battery terminals. Discharged sulfate batteries tend to degrade by sulfating, which involves the formation of large lead-sulfate crystals in the batteries. But, I found out that this not the case. I have heard that pulling off one of the battery cables, while engine is running, is a good test to tell if the alternator or battery is bad. The slippage also produces heat that can harm the front alternator bearing and damage the drive belt. Alternator/generator/regulator problem of the 1997 Lincoln Town Car 6. A wide variety of problems can cause weird noises in your car, but a failing alternator is a likely culprit. The failing alternator symptom most drivers recognize is dim or flickering lights. Charging voltage: With the engine running steadily, A reading between 13. I started a Polaris atv without a battery and it blew every light bulb, because the battery was removed to stop the unwanted voltage. It's easy to tell when your car is having problems, but figuring out the cause of those problems can get confusing. 00 difference and if I were to fix the wrong one, I would still be left without a running car. If the dashboard gradually dims, the alternator is likely at fault. Take it to a parts shop that has a roll-out or hand-held alternator/battery tester. While running the volt meter showed 12. If there is an irregular sound like screeching or a squealing, then it is a visible sign of trouble. Please Settle a bet. At the other extreme, a battery that is sulfated due to being undercharged or not seeing constant use will maintain normal charging voltages. Alternator slippage and undercharging can also be caused by a bad alternator pulley. More specifically, the voltage regulator is part of the charging system responsible for managing the output of the alternator and maintaining a full charge on the battery. No, it would be to see how the belt runs between the engine an alternator, and whether the tensioner is all running true, as well as whether I can pull start it easily enough when it's also turning the belt and alternator. A dead alternator can cause all kinds of headaches, but how can you tell if your alternator is going out before it is too late? When you try to start your car and you hear a clicking sound, that signals your vehicle is dead you are left with several options as to why. Without it, your car will run off of battery power until it is discharged and then shut down. c) Alternator fault - Can be checked and repaired d) Wiring fault - Can be checked and repaired. The battery gets topped up and then just sits there waiting for the next time you start the car. If your car starts but immediately dies after, then your alternator needs checking. If it's in the range, it's good. An alternator that can put out more amps does no damage to your system. Now the belt squeaks. Check if battery is charged o rule out bad battery. It is not uncommon for a "noisy" alternator to cause the engine to run funny. A bosch alternator, for instance, has an exellent warantee and is rebuilt with all of the most important components. If nothing obvious can be found, pull alternator and have it checked on a machine. A faulty or unreliable charging system can also drain the battery while the car is running. 64 v each time so I feel confident that it is getting enough voltage to charge while driving. To prevent more failing of your electrical system, a bad alternator can easily strain the battery power, as an example, see. even though with the car running, your alternator is putting out around 13. I'd at least check the alternator main output terminal. A good voltage while the car is off and has not been running for a few hours (idle voltage) is ~>=12. If you can jumpstart your car and it stays running, your battery is out of service. Having this happen on the side of a busy road or highway can create a lot of problems. An alternator charges your battery when the car is running. It can test AGM, GEL or Lead Acid and can test charging systems 12 and 24 volts. If your car continues to run with only the positive terminal connected, your battery is bad and won’t hold a charge. At 100mph On Track For The First Time Blog 3 Bad Biker Habits I. I also went to AutoZone, where they tested for free, first test came up battery no good. The final stage of the alternator’s construction is the use of diodes within a rectifier. If your alternator is not in optimal running condition, other components can be damaged! This can mean expensive repairs, inconvenience, or even break downs. There are two simple tests you can perform to determine if your car's alternator is going bad: a headlight test and a battery test. With engine off and after sitting for a few minutes, meter reads 12. reserve, that means the battery will last that long before it is completely deadit also depends on how old the battery is and how many accessories that you have running as well, like everyone else said, if you alternator is out, do not use your headlights, the a/c or heater and when you come to a stoplight, put it. In other words, a bad alternator can get your attention by killing your car's battery,.